This invention relates to the technology of decomposing and refining large volumes of hairs and feathers using fungi. The invention also relates to the technology of using as fertilizers the hairs and feathers that have been decomposed and refined by treatment with fungi.
In leather production, hairs must be removed from hides before they are further processed. One of the common unhairing methods is by dissolving hairs in sulfides and lime. Worldwide, at least several tens of thousand tons of hairs are annually treated (see, for example, U.S. Leather Industries Statistics 1995) and the liquid wastes from the unhairing step account for most of the pollutants in the effluent streams from leather production.
To deal with this situation, a so-called xe2x80x9chair saving unhairing processxe2x80x9d has recently been commercialized that can remove hairs with a reduced amount of sulfides (see xe2x80x9cDevelopment and Research of Non-Chrome Tanning Technologiesxe2x80x9d, A 1995 Report of Projects Commissioned by MITI, published by the Japanese Association of Leather Technology, Mar. 30, 1996). The method is capable of reducing pollutants in effluent streams but, on the other hand, waste hairs that are conventionally solubilized and disposed of are recovered as solids. Since the hair is slightly decomposable, no effective method for treating the waste hairs has been established.
Large amounts of feathers occur in the poultry industry. Most of them are disposed of and some are used as feeds; however, the feeds from waste feathers are too costly to be considered as a commercially feasible utilization of resources.
Both hairs and feathers are fibrous and structurally so rigid that they cannot immediately be used as raw materials. Making powders of hairs and feathers is advantageous for their effective use in various fields. However, dry grinding of hairs and feathers is not capable of imparting the necessary impact to them which are lightweight and soft. In addition, they are so rigid in structure that they cannot be ground without applying strong external forces. Wet grinding methods developed so far include cutting hairs or feathers into suitable lengths and pulverizing them into powder over a prolonged time, or heating them under pressure and thereafter swelling them to become modified and making a powder of them (see, for example, Unexamined Published Japanese Patent Application (kokai) No. 207855/1990 describing an invention entitled xe2x80x9cProcess for Producing Hair Powdersxe2x80x9d). However, treating large volumes of hairs and feathers by those conventional methods is too costly and requires too large facilities to be implemented on a commercial scale.
Unexamined Published German Patent Application No. 1,090,673 discloses a method of performing proteolysis on hairs and feathers with Streptomyces fradiae to make them water-soluble. However, this method not only fails to solve the problem of polluted effluent streams from leather production; it is also unsuitable for the purpose of treating hairs and feathers in large volumes.
In short, no technology has yet been established to provide a method by which large waste hairs that result from the hair saving unhairing process and feathers that occur in the poultry industry can be treated conveniently at low cost, with the added capability for making effective use of them.
An object, therefore, of the invention is to provide a technology capable of high-volume treatment of waste hairs that occur massively in leather production, as well as feathers that derive from the poultry industry. In other words, the invention aims at treating large volumes of hairs and feathers conveniently at low cost and making effective use of the resulting decomposed and refined product.
With a view to attaining the stated objects, the present inventors made intensive studies and found that certain fungal species could grow by feeding on hairs or feathers as a nutrient source and that the hairs or feathers eventually decomposed and became refined to a readily available state. The present invention has been accomplished on the basis of these findings.
Hence, according to its first aspect, the invention provides a method of decomposing and refining hairs or feathers by treating them in an oxygen-containing gas stream with a fungus that is aerobic and can decompose hairs and feathers.
According to its second aspect, the invention provides the product of decomposition and refining of hairs or feathers that is obtained by the method.
The present inventors also found that the thus obtained product of decomposition and refining of hairs or feathers is useful as a fertilizer. Therefore, according to its third aspect, the invention provides a fertilizer containing such product of decomposition and refining of hairs or feathers.